This series adds the kernel's build ID[1] to the stacktrace header printed
in oops messages, warnings, etc. and the build ID for any module that
appears in the stacktrace after the module name. The goal is to make the
stacktrace more self-contained and descriptive by including the relevant
build IDs in the kernel logs when something goes wrong. This can be used
by post processing tools like script/decode_stacktrace.sh and kernel
developers to easily locate the debug info associated with a kernel
crash and line up what line and file things started falling apart at.
To show how this can be used I've included a patch to
decode_stacktrace.sh that downloads the debuginfo from a debuginfod
server.
This also includes some patches to make the buildid.c file use more
const arguments and consolidate logic into buildid.c from kdump. These
are left to the end as they were mostly cleanup patches. I don't know
who exactly maintains this so I guess Andrew is the best option to merge
all this code.
Here's an example lkdtm stacktrace on arm64.
WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE
CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1
Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--)
pc : lkdtm_WARNING+0x28/0x30 [lkdtm]
lr : lkdtm_do_action+0x24/0x40 [lkdtm]
sp : ffffffc0134fbca0
x29: ffffffc0134fbca0 x28: ffffff92d53ba240
x27: 0000000000000000 x26: 0000000000000000
x25: 0000000000000000 x24: ffffffe3622352c0
x23: 0000000000000020 x22: ffffffe362233366
x21: ffffffe3622352e0 x20: ffffffc0134fbde0
x19: 0000000000000008 x18: 0000000000000000
x17: ffffff929b6536fc x16: 0000000000000000
x15: 0000000000000000 x14: 0000000000000012
x13: ffffffe380ed892c x12: ffffffe381d05068
x11: 0000000000000000 x10: 0000000000000000
x9 : 0000000000000001 x8 : ffffffe362237000
x7 : aaaaaaaaaaaaaaaa x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001
x3 : 0000000000000008 x2 : ffffff93fef25a70
x1 : ffffff93fef15788 x0 : ffffffe3622352e0
Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8
ksys_write+0x84/0xf0
__arm64_sys_write+0x24/0x30
el0_svc_common+0xf4/0x1c0
do_el0_svc_compat+0x28/0x3c
el0_svc_compat+0x10/0x1c
el0_sync_compat_handler+0xa8/0xcc
el0_sync_compat+0x178/0x180
---[ end trace 3d95032303e59e68 ]---
Changes from v1 (https://lore.kernel.org/r/[email protected]):
* New printk format %pSb and %pSr
* Return binary format instead of hex format string from build ID APIs
* Some new patches to cleanup buildid/decode_stacktrace.sh
* A new patch to decode_stacktrace.sh to parse output
[1] https://fedoraproject.org/wiki/Releases/FeatureBuildId
Cc: Alexei Starovoitov <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: <[email protected]>
Stephen Boyd (12):
buildid: Add API to parse build ID out of buffer
buildid: Add method to get running kernel's build ID
dump_stack: Add vmlinux build ID to stack traces
module: Add printk format to add module build ID to stacktraces
arm64: stacktrace: Use %pSb for backtrace printing
x86/dumpstack: Use %pSb for backtrace printing
scripts/decode_stacktrace.sh: Support debuginfod
scripts/decode_stacktrace.sh: Silence stderr messages from
addr2line/nm
scripts/decode_stacktrace.sh: Indicate 'auto' can be used for base
path
buildid: Mark some arguments const
buildid: Fix kernel-doc notation
kdump: Use vmlinux_build_id() to simplify
Documentation/core-api/printk-formats.rst | 9 +++
arch/arm64/kernel/stacktrace.c | 2 +-
arch/x86/kernel/dumpstack.c | 4 +-
include/linux/buildid.h | 3 +
include/linux/crash_core.h | 6 +-
include/linux/kallsyms.h | 13 +++-
include/linux/module.h | 6 +-
kernel/crash_core.c | 41 +----------
kernel/kallsyms.c | 73 ++++++++++++++-----
kernel/module.c | 24 +++++-
lib/buildid.c | 75 +++++++++++++++----
lib/dump_stack.c | 5 +-
lib/vsprintf.c | 6 +-
scripts/decode_stacktrace.sh | 89 +++++++++++++++++++----
14 files changed, 251 insertions(+), 105 deletions(-)
base-commit: a38fd8748464831584a19438cbb3082b5a2dab15
--
https://chromeos.dev
Let's use the new printk format to print the stacktrace entry when
printing a backtrace to the kernel logs. This will include any module's
build ID[1] in it so that offline/crash debugging can easily locate the
debuginfo for a module via something like debuginfod[2].
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1]
Link: https://sourceware.org/elfutils/Debuginfod.html [2]
Signed-off-by: Stephen Boyd <[email protected]>
---
arch/arm64/kernel/stacktrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index ad20981dfda4..9d38da01ff98 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -129,7 +129,7 @@ NOKPROBE_SYMBOL(walk_stackframe);
static void dump_backtrace_entry(unsigned long where, const char *loglvl)
{
- printk("%s %pS\n", loglvl, (void *)where);
+ printk("%s %pSb\n", loglvl, (void *)where);
}
void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
--
https://chromeos.dev
Now that stacktraces contain the build ID information we can update this
script to use debuginfod-find to locate the debuginfo for the vmlinux
and modules automatically. This can replace the existing code that
requires specifying a path to vmlinux or tries to find the vmlinux and
modules automatically by using the release number. Work it into the
script as a fallback option if the vmlinux isn't specified on the
commandline.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
scripts/decode_stacktrace.sh | 81 +++++++++++++++++++++++++++++++-----
1 file changed, 70 insertions(+), 11 deletions(-)
diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index 90398347e366..ca21f8bdf5f2 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -3,11 +3,10 @@
# (c) 2014, Sasha Levin <[email protected]>
#set -x
-if [[ $# < 1 ]]; then
+usage() {
echo "Usage:"
echo " $0 -r <release> | <vmlinux> [base path] [modules path]"
- exit 1
-fi
+}
if [[ $1 == "-r" ]] ; then
vmlinux=""
@@ -24,6 +23,7 @@ if [[ $1 == "-r" ]] ; then
if [[ $vmlinux == "" ]] ; then
echo "ERROR! vmlinux image for release $release is not found" >&2
+ usage
exit 2
fi
else
@@ -31,12 +31,35 @@ else
basepath=${2-auto}
modpath=$3
release=""
+ debuginfod=
+
+ # Can we use debuginfod-find?
+ if type debuginfod-find >/dev/null 2>&1 ; then
+ debuginfod=${1-only}
+ fi
+
+ if [[ $vmlinux == "" && -z $debuginfod ]] ; then
+ echo "ERROR! vmlinux image must be specified" >&2
+ usage
+ exit 1
+ fi
fi
declare -A cache
declare -A modcache
find_module() {
+ if [[ -n $debuginfod ]] ; then
+ if [[ -n $modbuildid ]] ; then
+ debuginfod-find debuginfo $modbuildid && return
+ fi
+
+ # Only using debuginfod so don't try to find vmlinux module path
+ if [[ $debuginfod == "only" ]] ; then
+ return
+ fi
+ fi
+
if [[ "$modpath" != "" ]] ; then
for fn in $(find "$modpath" -name "${module//_/[-_]}.ko*") ; do
if readelf -WS "$fn" | grep -qwF .debug_line ; then
@@ -150,6 +173,27 @@ parse_symbol() {
symbol="$segment$name ($code)"
}
+debuginfod_get_vmlinux() {
+ local vmlinux_buildid=${1##* }
+
+ if [[ $vmlinux != "" ]]; then
+ return
+ fi
+
+ if [[ $vmlinux_buildid =~ ^[0-9a-f]+ ]]; then
+ vmlinux=$(debuginfod-find debuginfo $vmlinux_buildid)
+ if [[ $? -ne 0 ]] ; then
+ echo "ERROR! vmlinux image not found via debuginfod-find" >&2
+ usage
+ exit 2
+ fi
+ return
+ fi
+ echo "ERROR! Build ID for vmlinux not found. Try passing -r or specifying vmlinux" >&2
+ usage
+ exit 2
+}
+
decode_code() {
local scripts=`dirname "${BASH_SOURCE[0]}"`
@@ -157,6 +201,14 @@ decode_code() {
}
handle_line() {
+ if [[ $basepath == "auto" && $vmlinux != "" ]] ; then
+ module=""
+ symbol="kernel_init+0x0/0x0"
+ parse_symbol
+ basepath=${symbol#kernel_init (}
+ basepath=${basepath%/init/main.c:*)}
+ fi
+
local words
# Tokenize
@@ -182,16 +234,28 @@ handle_line() {
fi
done
+ if [[ ${words[$last]} =~ ^[0-9a-f]+\] ]]; then
+ words[$last-1]="${words[$last-1]} ${words[$last]}"
+ unset words[$last]
+ last=$(( $last - 1 ))
+ fi
+
if [[ ${words[$last]} =~ \[([^]]+)\] ]]; then
module=${words[$last]}
module=${module#\[}
module=${module%\]}
+ modbuildid=${module#* }
+ module=${module% *}
+ if [[ $modbuildid == $module ]]; then
+ modbuildid=
+ fi
symbol=${words[$last-1]}
unset words[$last-1]
else
# The symbol is the last element, process it
symbol=${words[$last]}
module=
+ modbuildid=
fi
unset words[$last]
@@ -201,14 +265,6 @@ handle_line() {
echo "${words[@]}" "$symbol $module"
}
-if [[ $basepath == "auto" ]] ; then
- module=""
- symbol="kernel_init+0x0/0x0"
- parse_symbol
- basepath=${symbol#kernel_init (}
- basepath=${basepath%/init/main.c:*)}
-fi
-
while read line; do
# Let's see if we have an address in the line
if [[ $line =~ \[\<([^]]+)\>\] ]] ||
@@ -218,6 +274,9 @@ while read line; do
# Is it a code line?
elif [[ $line == *Code:* ]]; then
decode_code "$line"
+ # Is it a version line?
+ elif [[ -n $debuginfod && $line =~ PID:\ [0-9]+\ Comm: ]]; then
+ debuginfod_get_vmlinux "$line"
else
# Nothing special in this line, show it as is
echo "$line"
--
https://chromeos.dev
These arguments are never modified so they can be marked const to
indicate as such.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
lib/buildid.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/lib/buildid.c b/lib/buildid.c
index fa1b6466b4b8..1a35b28a85d8 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -47,10 +47,10 @@ static int parse_build_id_buf(unsigned char *build_id,
return -EINVAL;
}
-static inline int parse_build_id(void *page_addr,
+static inline int parse_build_id(const void *page_addr,
unsigned char *build_id,
__u32 *size,
- void *note_start,
+ const void *note_start,
Elf32_Word note_size)
{
/* check for overflow */
@@ -65,7 +65,7 @@ static inline int parse_build_id(void *page_addr,
}
/* Parse build ID from 32-bit ELF */
-static int get_build_id_32(void *page_addr, unsigned char *build_id,
+static int get_build_id_32(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
@@ -90,7 +90,7 @@ static int get_build_id_32(void *page_addr, unsigned char *build_id,
}
/* Parse build ID from 64-bit ELF */
-static int get_build_id_64(void *page_addr, unsigned char *build_id,
+static int get_build_id_64(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
--
https://chromeos.dev
On Tue, Mar 23, 2021 at 07:04:31PM -0700, Stephen Boyd wrote:
> x5 : 0000000000000000 x4 : 0000000000000001
> x3 : 0000000000000008 x2 : ffffff93fef25a70
> x1 : ffffff93fef15788 x0 : ffffffe3622352e0
> Call trace:
> lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
Yikes. No, please do not make the backtraces a complete mess for
something that serves absolutely no need.
Let's make kernel stacktraces easier to identify by including the build
ID[1] of a module if the stacktrace is printing a symbol from a module.
This makes it simpler for developers to locate a kernel module's full
debuginfo for a particular stacktrace. Combined with
scripts/decode_stracktrace.sh, a developer can download the matching
debuginfo from a debuginfod[2] server and find the exact file and line
number for the functions plus offsets in a stacktrace that match the
module. This is especially useful for pstore crash debugging where the
kernel crashes are recorded in something like console-ramoops and the
recovery kernel/modules are different or the debuginfo doesn't exist on
the device due to space concerns (the debuginfo can be too large for
space limited devices).
Originally, I put this on the %pS format, but that was quickly rejected
given that %pS is used in other places such as ftrace where build IDs
aren't meaningful. There was some discussions on the list to put every
module build ID into the "Modules linked in:" section of the stacktrace
message but that quickly becomes very hard to read once you have more
than three or four modules linked in. It also provides too much
information when we don't expect each module to be traversed in a
stacktrace. Having the build ID for modules that aren't important just
makes things messy. Splitting it to multiple lines for each module
quickly explodes the number of lines printed in an oops too, possibly
wrapping the warning off the console. And finally, trying to stash away
each module used in a callstack to provide the ID of each symbol printed
is cumbersome and would require changes to each architecture to stash
away modules and return their build IDs once unwinding has completed.
Instead, we opt for the simpler approach of introducing a new printk
format '%p[sS][br]' for "pointer symbolic backtrace with module build ID"
and then updating the few places in the architecture layer where the
stacktrace is printed to use this new format.
Example:
WARNING: CPU: 3 PID: 3373 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE hci_uart <modules trimmed>
CPU: 3 PID: 3373 Comm: bash Not tainted 5.11 #12 a8c0d47f7051f3e6670ceaea724af66a39c6cec8
Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--)
pc : lkdtm_WARNING+0x28/0x30 [lkdtm]
lr : lkdtm_do_action+0x24/0x40 [lkdtm]
sp : ffffffc013febca0
x29: ffffffc013febca0 x28: ffffff88d9438040
x27: 0000000000000000 x26: 0000000000000000
x25: 0000000000000000 x24: ffffffdd0e9772c0
x23: 0000000000000020 x22: ffffffdd0e975366
x21: ffffffdd0e9772e0 x20: ffffffc013febde0
x19: 0000000000000008 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000037
x15: ffffffdd102ab174 x14: 0000000000000003
x13: 0000000000000004 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000
x9 : 0000000000000001 x8 : ffffffdd0e979000
x7 : 0000000000000000 x6 : ffffffdd10ff6b54
x5 : 0000000000000000 x4 : 0000000000000000
x3 : ffffffc013feb938 x2 : ffffff89fef05a70
x1 : ffffff89feef5788 x0 : ffffffdd0e9772e0
Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
direct_entry+0x16c/0x1b4 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8
ksys_write+0x84/0xf0
__arm64_sys_write+0x24/0x30
el0_svc_common+0xf4/0x1c0
do_el0_svc_compat+0x28/0x3c
el0_svc_compat+0x10/0x1c
el0_sync_compat_handler+0xa8/0xcc
el0_sync_compat+0x178/0x180
---[ end trace f89bc7f5417cbcc6 ]---
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1]
Link: https://sourceware.org/elfutils/Debuginfod.html [2]
Signed-off-by: Stephen Boyd <[email protected]>
---
Documentation/core-api/printk-formats.rst | 9 +++
include/linux/kallsyms.h | 13 +++-
include/linux/module.h | 6 +-
kernel/kallsyms.c | 73 ++++++++++++++++-------
kernel/module.c | 24 +++++++-
lib/vsprintf.c | 6 +-
6 files changed, 106 insertions(+), 25 deletions(-)
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 160e710d992f..c0844cb275eb 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -114,6 +114,15 @@ used when printing stack backtraces. The specifier takes into
consideration the effect of compiler optimisations which may occur
when tail-calls are used and marked with the noreturn GCC attribute.
+If the pointer is within a module, the module name and optionally build ID is
+printed after the symbol name.
+
+::
+ %pS versatile_init+0x0/0x110 [module_name]
+ %pSb versatile_init+0x0/0x110 [module_name ed5019fdf5e53be37cb1ba7899292d7e143b259e]
+ %pSr versatile_init+0x9/0x110 [module_name ed5019fdf5e53be37cb1ba7899292d7e143b259e]
+ (with __builtin_extract_return_addr() translation)
+
Probed Pointers from BPF / tracing
----------------------------------
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 465060acc981..9f489aaa4127 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -7,6 +7,7 @@
#define _LINUX_KALLSYMS_H
#include <linux/errno.h>
+#include <linux/buildid.h>
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/mm.h>
@@ -15,8 +16,9 @@
#include <asm/sections.h>
#define KSYM_NAME_LEN 128
-#define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + (KSYM_NAME_LEN - 1) + \
- 2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + 1)
+#define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s %s]") + (KSYM_NAME_LEN - 1) + \
+ 2*(BITS_PER_LONG*3/10) + (MODULE_NAME_LEN - 1) + \
+ (BUILD_ID_SIZE_MAX * 2) + 1)
struct cred;
struct module;
@@ -91,6 +93,7 @@ const char *kallsyms_lookup(unsigned long addr,
/* Look up a kernel symbol and return it in a text buffer. */
extern int sprint_symbol(char *buffer, unsigned long address);
+extern int sprint_symbol_stacktrace(char *buffer, unsigned long address);
extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
extern int sprint_backtrace(char *buffer, unsigned long address);
@@ -128,6 +131,12 @@ static inline int sprint_symbol(char *buffer, unsigned long addr)
return 0;
}
+static inline int sprint_symbol_stacktrace(char *buffer, unsigned long address)
+{
+ *buffer = '\0';
+ return 0;
+}
+
static inline int sprint_symbol_no_offset(char *buffer, unsigned long addr)
{
*buffer = '\0';
diff --git a/include/linux/module.h b/include/linux/module.h
index 59f094fa6f74..0d17c7eb4c8a 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -11,6 +11,7 @@
#include <linux/list.h>
#include <linux/stat.h>
+#include <linux/buildid.h>
#include <linux/compiler.h>
#include <linux/cache.h>
#include <linux/kmod.h>
@@ -367,6 +368,9 @@ struct module {
/* Unique handle for this module */
char name[MODULE_NAME_LEN];
+ /* Module build ID */
+ unsigned char build_id[BUILD_ID_SIZE_MAX];
+
/* Sysfs stuff. */
struct module_kobject mkobj;
struct module_attribute *modinfo_attrs;
@@ -630,7 +634,7 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr);
const char *module_address_lookup(unsigned long addr,
unsigned long *symbolsize,
unsigned long *offset,
- char **modname,
+ char **modname, unsigned char **modbuildid,
char *namebuf);
int lookup_module_symbol_name(unsigned long addr, char *symname);
int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 8043a90aa50e..e77a1b6680a9 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -273,21 +273,13 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
get_symbol_pos(addr, symbolsize, offset);
return 1;
}
- return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
+ return !!module_address_lookup(addr, symbolsize, offset, NULL, NULL, namebuf) ||
!!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
}
-/*
- * Lookup an address
- * - modname is set to NULL if it's in the kernel.
- * - We guarantee that the returned name is valid until we reschedule even if.
- * It resides in a module.
- * - We also guarantee that modname will be valid until rescheduled.
- */
-const char *kallsyms_lookup(unsigned long addr,
- unsigned long *symbolsize,
- unsigned long *offset,
- char **modname, char *namebuf)
+const char *kallsyms_lookup_buildid(unsigned long addr, unsigned long *symbolsize,
+ unsigned long *offset, char **modname,
+ unsigned char **modbuildid, char *namebuf)
{
const char *ret;
@@ -303,12 +295,14 @@ const char *kallsyms_lookup(unsigned long addr,
namebuf, KSYM_NAME_LEN);
if (modname)
*modname = NULL;
+ if (modbuildid)
+ *modbuildid = NULL;
return namebuf;
}
/* See if it's in a module or a BPF JITed image. */
ret = module_address_lookup(addr, symbolsize, offset,
- modname, namebuf);
+ modname, modbuildid, namebuf);
if (!ret)
ret = bpf_address_lookup(addr, symbolsize,
offset, modname, namebuf);
@@ -319,6 +313,22 @@ const char *kallsyms_lookup(unsigned long addr,
return ret;
}
+/*
+ * Lookup an address
+ * - modname is set to NULL if it's in the kernel.
+ * - We guarantee that the returned name is valid until we reschedule even if.
+ * It resides in a module.
+ * - We also guarantee that modname will be valid until rescheduled.
+ */
+const char *kallsyms_lookup(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname, char *namebuf)
+{
+ return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,
+ NULL, namebuf);
+}
+
int lookup_symbol_name(unsigned long addr, char *symname)
{
symname[0] = '\0';
@@ -359,15 +369,17 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
/* Look up a kernel symbol and return it in a text buffer. */
static int __sprint_symbol(char *buffer, unsigned long address,
- int symbol_offset, int add_offset)
+ int symbol_offset, int add_offset, int add_buildid)
{
char *modname;
+ unsigned char *buildid;
const char *name;
unsigned long offset, size;
int len;
address += symbol_offset;
- name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
+ name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,
+ buffer);
if (!name)
return sprintf(buffer, "0x%lx", address - symbol_offset);
@@ -379,8 +391,12 @@ static int __sprint_symbol(char *buffer, unsigned long address,
if (add_offset)
len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
- if (modname)
- len += sprintf(buffer + len, " [%s]", modname);
+ if (modname) {
+ len += sprintf(buffer + len, " [%s", modname);
+ if (add_buildid && buildid)
+ len += sprintf(buffer + len, " %20phN", buildid);
+ len += sprintf(buffer + len, "]");
+ }
return len;
}
@@ -398,10 +414,27 @@ static int __sprint_symbol(char *buffer, unsigned long address,
*/
int sprint_symbol(char *buffer, unsigned long address)
{
- return __sprint_symbol(buffer, address, 0, 1);
+ return __sprint_symbol(buffer, address, 0, 1, 0);
}
EXPORT_SYMBOL_GPL(sprint_symbol);
+/**
+ * sprint_symbol_stacktrace - Look up a kernel symbol and return it in a text buffer
+ * @buffer: buffer to be stored
+ * @address: address to lookup
+ *
+ * This function looks up a kernel symbol with @address and stores its name,
+ * offset, size, module name and module build ID to @buffer if possible. If no
+ * symbol was found, just saves its @address as is.
+ *
+ * This function returns the number of bytes stored in @buffer.
+ */
+int sprint_symbol_stacktrace(char *buffer, unsigned long address)
+{
+ return __sprint_symbol(buffer, address, 0, 1, 1);
+}
+EXPORT_SYMBOL_GPL(sprint_symbol_stacktrace);
+
/**
* sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
* @buffer: buffer to be stored
@@ -415,7 +448,7 @@ EXPORT_SYMBOL_GPL(sprint_symbol);
*/
int sprint_symbol_no_offset(char *buffer, unsigned long address)
{
- return __sprint_symbol(buffer, address, 0, 0);
+ return __sprint_symbol(buffer, address, 0, 0, 0);
}
EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
@@ -435,7 +468,7 @@ EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
*/
int sprint_backtrace(char *buffer, unsigned long address)
{
- return __sprint_symbol(buffer, address, -1, 1);
+ return __sprint_symbol(buffer, address, -1, 1, 0);
}
/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
diff --git a/kernel/module.c b/kernel/module.c
index 30479355ab85..9e9cb502fb33 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -13,6 +13,7 @@
#include <linux/trace_events.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
+#include <linux/buildid.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/sysfs.h>
@@ -2770,6 +2771,20 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
}
mod->core_kallsyms.num_symtab = ndst;
}
+
+static void init_build_id(struct module *mod, const struct load_info *info)
+{
+ const Elf_Shdr *sechdr;
+ unsigned int i;
+
+ for (i = 0; i < info->hdr->e_shnum; i++) {
+ sechdr = &info->sechdrs[i];
+ if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
+ !build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
+ sechdr->sh_size))
+ break;
+ }
+}
#else
static inline void layout_symtab(struct module *mod, struct load_info *info)
{
@@ -2778,6 +2793,10 @@ static inline void layout_symtab(struct module *mod, struct load_info *info)
static void add_kallsyms(struct module *mod, const struct load_info *info)
{
}
+
+static void init_build_id(struct module *mod, const struct load_info *info)
+{
+}
#endif /* CONFIG_KALLSYMS */
static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsigned int num)
@@ -4004,6 +4023,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
goto free_arch_cleanup;
}
+ init_build_id(mod, info);
dynamic_debug_setup(mod, info->debug, info->num_debug);
/* Ftrace init must be called in the MODULE_STATE_UNFORMED state */
@@ -4235,7 +4255,7 @@ void * __weak dereference_module_function_descriptor(struct module *mod,
const char *module_address_lookup(unsigned long addr,
unsigned long *size,
unsigned long *offset,
- char **modname,
+ char **modname, unsigned char **modbuildid,
char *namebuf)
{
const char *ret = NULL;
@@ -4246,6 +4266,8 @@ const char *module_address_lookup(unsigned long addr,
if (mod) {
if (modname)
*modname = mod->name;
+ if (modbuildid)
+ *modbuildid = mod->build_id;
ret = find_kallsyms_symbol(mod, addr, size, offset);
}
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 41ddc353ebb8..9cd62e84e4aa 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -961,13 +961,15 @@ char *symbol_string(char *buf, char *end, void *ptr,
char sym[KSYM_SYMBOL_LEN];
#endif
- if (fmt[1] == 'R')
+ if (fmt[1] == 'R' || fmt[1] == 'r')
ptr = __builtin_extract_return_addr(ptr);
value = (unsigned long)ptr;
#ifdef CONFIG_KALLSYMS
if (*fmt == 'B')
sprint_backtrace(sym, value);
+ else if (*fmt == 'S' && (fmt[1] == 'b' || fmt[1] == 'r'))
+ sprint_symbol_stacktrace(sym, value);
else if (*fmt != 's')
sprint_symbol(sym, value);
else
@@ -2129,6 +2131,8 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
* - 'S' For symbolic direct pointers (or function descriptors) with offset
* - 's' For symbolic direct pointers (or function descriptors) without offset
* - '[Ss]R' as above with __builtin_extract_return_addr() translation
+ * - '[Ss]r' as above with __builtin_extract_return_addr() translation and module build ID
+ * - '[Ss]b' as above with module build ID (for use in backtraces)
* - '[Ff]' %pf and %pF were obsoleted and later removed in favor of
* %ps and %pS. Be careful when re-using these specifiers.
* - 'B' For backtraced symbolic direct pointers with offset
--
https://chromeos.dev
Add an API that can parse the build ID out of a buffer, instead of a
vma, to support printing a kernel module's build ID for stack traces.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
include/linux/buildid.h | 1 +
lib/buildid.c | 50 ++++++++++++++++++++++++++++++-----------
2 files changed, 38 insertions(+), 13 deletions(-)
diff --git a/include/linux/buildid.h b/include/linux/buildid.h
index 40232f90db6e..ebce93f26d06 100644
--- a/include/linux/buildid.h
+++ b/include/linux/buildid.h
@@ -8,5 +8,6 @@
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
__u32 *size);
+int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
#endif
diff --git a/lib/buildid.c b/lib/buildid.c
index 6156997c3895..010ab0674cb9 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -2,30 +2,23 @@
#include <linux/buildid.h>
#include <linux/elf.h>
+#include <linux/kernel.h>
#include <linux/pagemap.h>
#define BUILD_ID 3
+
/*
* Parse build id from the note segment. This logic can be shared between
* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
* identical.
*/
-static inline int parse_build_id(void *page_addr,
- unsigned char *build_id,
- __u32 *size,
- void *note_start,
- Elf32_Word note_size)
+static int parse_build_id_buf(unsigned char *build_id,
+ __u32 *size,
+ const void *note_start,
+ Elf32_Word note_size)
{
Elf32_Word note_offs = 0, new_offs;
- /* check for overflow */
- if (note_start < page_addr || note_start + note_size < note_start)
- return -EINVAL;
-
- /* only supports note that fits in the first page */
- if (note_start + note_size > page_addr + PAGE_SIZE)
- return -EINVAL;
-
while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
@@ -49,9 +42,27 @@ static inline int parse_build_id(void *page_addr,
break;
note_offs = new_offs;
}
+
return -EINVAL;
}
+static inline int parse_build_id(void *page_addr,
+ unsigned char *build_id,
+ __u32 *size,
+ void *note_start,
+ Elf32_Word note_size)
+{
+ /* check for overflow */
+ if (note_start < page_addr || note_start + note_size < note_start)
+ return -EINVAL;
+
+ /* only supports note that fits in the first page */
+ if (note_start + note_size > page_addr + PAGE_SIZE)
+ return -EINVAL;
+
+ return parse_build_id_buf(build_id, size, note_start, note_size);
+}
+
/* Parse build ID from 32-bit ELF */
static int get_build_id_32(void *page_addr, unsigned char *build_id,
__u32 *size)
@@ -147,3 +158,16 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
put_page(page);
return ret;
}
+
+/**
+ * build_id_parse_buf - Get build ID from a buffer
+ * @buf: Elf note section(s) to parse
+ * @buf_size: Size of @buf in bytes
+ * @build_id: Build ID parsed from @buf, at least BUILD_ID_SIZE_MAX long
+ *
+ * Return: 0 on success, -EINVAL otherwise
+ */
+int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
+{
+ return parse_build_id_buf(build_id, NULL, buf, buf_size);
+}
--
https://chromeos.dev
Add "auto" to the usage message so that it's a little clearer that you
can pass "auto" as the second argument. When passing "auto" the script
tries to find the base path automatically instead of requiring it be
passed on the commandline. Also use [<variable>] to indicate the
variable argument and that it is optional so that we can differentiate
from the literal "auto" that should be passed.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
scripts/decode_stacktrace.sh | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index 20b5af1ebe5e..5fbad61fe490 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -5,7 +5,7 @@
usage() {
echo "Usage:"
- echo " $0 -r <release> | <vmlinux> [base path] [modules path]"
+ echo " $0 -r <release> | <vmlinux> [<base path>|auto] [<modules path>]"
}
if [[ $1 == "-r" ]] ; then
--
https://chromeos.dev
Kernel doc should use "Return:" instead of "Returns" to properly reflect
the return values.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
lib/buildid.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/buildid.c b/lib/buildid.c
index 1a35b28a85d8..f797e4439bda 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -120,7 +120,7 @@ static int get_build_id_64(const void *page_addr, unsigned char *build_id,
* @build_id: buffer to store build id, at least BUILD_ID_SIZE long
* @size: returns actual build id size in case of success
*
- * Returns 0 on success, otherwise error (< 0).
+ * Return: 0 on success, -EINVAL otherwise
*/
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
__u32 *size)
--
https://chromeos.dev
We can use the vmlinux_build_id() helper here now instead of open coding
it. This consolidates code and possibly avoids calculating the build ID
twice in the case of a crash with a stacktrace.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
include/linux/crash_core.h | 6 +-----
kernel/crash_core.c | 41 ++------------------------------------
2 files changed, 3 insertions(+), 44 deletions(-)
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 206bde8308b2..fb8ab99bb2ee 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -39,7 +39,7 @@ phys_addr_t paddr_vmcoreinfo_note(void);
#define VMCOREINFO_OSRELEASE(value) \
vmcoreinfo_append_str("OSRELEASE=%s\n", value)
#define VMCOREINFO_BUILD_ID(value) \
- vmcoreinfo_append_str("BUILD-ID=%s\n", value)
+ vmcoreinfo_append_str("BUILD-ID=%20phN\n", value)
#define VMCOREINFO_PAGESIZE(value) \
vmcoreinfo_append_str("PAGESIZE=%ld\n", value)
#define VMCOREINFO_SYMBOL(name) \
@@ -69,10 +69,6 @@ extern unsigned char *vmcoreinfo_data;
extern size_t vmcoreinfo_size;
extern u32 *vmcoreinfo_note;
-/* raw contents of kernel .notes section */
-extern const void __start_notes __weak;
-extern const void __stop_notes __weak;
-
Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
void *data, size_t data_len);
void final_note(Elf_Word *buf);
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 825284baaf46..0b0e24668697 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -4,6 +4,7 @@
* Copyright (C) 2002-2004 Eric Biederman <[email protected]>
*/
+#include <linux/buildid.h>
#include <linux/crash_core.h>
#include <linux/utsname.h>
#include <linux/vmalloc.h>
@@ -378,51 +379,13 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
}
EXPORT_SYMBOL(paddr_vmcoreinfo_note);
-#define NOTES_SIZE (&__stop_notes - &__start_notes)
-#define BUILD_ID_MAX SHA1_DIGEST_SIZE
-#define NT_GNU_BUILD_ID 3
-
-struct elf_note_section {
- struct elf_note n_hdr;
- u8 n_data[];
-};
-
/*
* Add build ID from .notes section as generated by the GNU ld(1)
* or LLVM lld(1) --build-id option.
*/
static void add_build_id_vmcoreinfo(void)
{
- char build_id[BUILD_ID_MAX * 2 + 1];
- int n_remain = NOTES_SIZE;
-
- while (n_remain >= sizeof(struct elf_note)) {
- const struct elf_note_section *note_sec =
- &__start_notes + NOTES_SIZE - n_remain;
- const u32 n_namesz = note_sec->n_hdr.n_namesz;
-
- if (note_sec->n_hdr.n_type == NT_GNU_BUILD_ID &&
- n_namesz != 0 &&
- !strcmp((char *)¬e_sec->n_data[0], "GNU")) {
- if (note_sec->n_hdr.n_descsz <= BUILD_ID_MAX) {
- const u32 n_descsz = note_sec->n_hdr.n_descsz;
- const u8 *s = ¬e_sec->n_data[n_namesz];
-
- s = PTR_ALIGN(s, 4);
- bin2hex(build_id, s, n_descsz);
- build_id[2 * n_descsz] = '\0';
- VMCOREINFO_BUILD_ID(build_id);
- return;
- }
- pr_warn("Build ID is too large to include in vmcoreinfo: %u > %u\n",
- note_sec->n_hdr.n_descsz,
- BUILD_ID_MAX);
- return;
- }
- n_remain -= sizeof(struct elf_note) +
- ALIGN(note_sec->n_hdr.n_namesz, 4) +
- ALIGN(note_sec->n_hdr.n_descsz, 4);
- }
+ VMCOREINFO_BUILD_ID(vmlinux_build_id());
}
static int __init crash_save_vmcoreinfo_init(void)
--
https://chromeos.dev
Sometimes if you're using tools that have linked things improperly or
have new features/sections that older tools don't expect you'll see
warnings printed to stderr. We don't really care about these warnings,
so let's just silence these messages to cleanup output of this script.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
---
scripts/decode_stacktrace.sh | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index ca21f8bdf5f2..20b5af1ebe5e 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -74,7 +74,7 @@ find_module() {
find_module && return
if [[ $release == "" ]] ; then
- release=$(gdb -ex 'print init_uts_ns.name.release' -ex 'quit' -quiet -batch "$vmlinux" | sed -n 's/\$1 = "\(.*\)".*/\1/p')
+ release=$(gdb -ex 'print init_uts_ns.name.release' -ex 'quit' -quiet -batch "$vmlinux" 2>/dev/null | sed -n 's/\$1 = "\(.*\)".*/\1/p')
fi
for dn in {/usr/lib/debug,}/lib/modules/$release ; do
@@ -128,7 +128,7 @@ parse_symbol() {
if [[ "${cache[$module,$name]+isset}" == "isset" ]]; then
local base_addr=${cache[$module,$name]}
else
- local base_addr=$(nm "$objfile" | awk '$3 == "'$name'" && ($2 == "t" || $2 == "T") {print $1; exit}')
+ local base_addr=$(nm "$objfile" 2>/dev/null | awk '$3 == "'$name'" && ($2 == "t" || $2 == "T") {print $1; exit}')
if [[ $base_addr == "" ]] ; then
# address not found
return
@@ -152,7 +152,7 @@ parse_symbol() {
if [[ "${cache[$module,$address]+isset}" == "isset" ]]; then
local code=${cache[$module,$address]}
else
- local code=$(${CROSS_COMPILE}addr2line -i -e "$objfile" "$address")
+ local code=$(${CROSS_COMPILE}addr2line -i -e "$objfile" "$address" 2>/dev/null)
cache[$module,$address]=$code
fi
--
https://chromeos.dev
Add the running kernel's build ID[1] to the stacktrace information
header. This makes it simpler for developers to locate the vmlinux with
full debuginfo for a particular kernel stacktrace. Combined with
scripts/decode_stracktrace.sh, a developer can download the correct
vmlinux from a debuginfod[2] server and find the exact file and line
number for the functions plus offsets in a stacktrace.
This is especially useful for pstore crash debugging where the kernel
crashes are recorded in the pstore logs and the recovery kernel is
different or the debuginfo doesn't exist on the device due to space
concerns (the data can be large and a security concern). The stacktrace
can be analyzed after the crash by using the build ID to find the
matching vmlinux and understand where in the function something went
wrong.
Example stacktrace from lkdtm:
WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE
CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1
Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--)
pc : lkdtm_WARNING+0x28/0x30 [lkdtm]
lr : lkdtm_do_action+0x24/0x40 [lkdtm]
sp : ffffffc0134fbca0
x29: ffffffc0134fbca0 x28: ffffff92d53ba240
x27: 0000000000000000 x26: 0000000000000000
x25: 0000000000000000 x24: ffffffe3622352c0
x23: 0000000000000020 x22: ffffffe362233366
x21: ffffffe3622352e0 x20: ffffffc0134fbde0
x19: 0000000000000008 x18: 0000000000000000
x17: ffffff929b6536fc x16: 0000000000000000
x15: 0000000000000000 x14: 0000000000000012
x13: ffffffe380ed892c x12: ffffffe381d05068
x11: 0000000000000000 x10: 0000000000000000
x9 : 0000000000000001 x8 : ffffffe362237000
x7 : aaaaaaaaaaaaaaaa x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001
x3 : 0000000000000008 x2 : ffffff93fef25a70
x1 : ffffff93fef15788 x0 : ffffffe3622352e0
Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm]
direct_entry+0x16c/0x1b4 [lkdtm]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8
ksys_write+0x84/0xf0
__arm64_sys_write+0x24/0x30
el0_svc_common+0xf4/0x1c0
do_el0_svc_compat+0x28/0x3c
el0_svc_compat+0x10/0x1c
el0_sync_compat_handler+0xa8/0xcc
el0_sync_compat+0x178/0x180
---[ end trace 3d95032303e59e68 ]---
The hex string aa23f7a1231c229de205662d5a9e0d4c580f19a1 is the build ID,
following the kernel version number.
Cc: Jiri Olsa <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Evan Green <[email protected]>
Cc: Hsin-Yi Wang <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1]
Link: https://sourceware.org/elfutils/Debuginfod.html [2]
Signed-off-by: Stephen Boyd <[email protected]>
---
lib/dump_stack.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index f5a33b6f773f..136bb942c4a3 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -5,6 +5,7 @@
*/
#include <linux/kernel.h>
+#include <linux/buildid.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
@@ -45,13 +46,13 @@ void __init dump_stack_set_arch_desc(const char *fmt, ...)
*/
void dump_stack_print_info(const char *log_lvl)
{
- printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s\n",
+ printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s %20phN\n",
log_lvl, raw_smp_processor_id(), current->pid, current->comm,
kexec_crash_loaded() ? "Kdump: loaded " : "",
print_tainted(),
init_utsname()->release,
(int)strcspn(init_utsname()->version, " "),
- init_utsname()->version);
+ init_utsname()->version, vmlinux_build_id());
if (dump_stack_arch_desc_str[0] != '\0')
printk("%sHardware name: %s\n",
--
https://chromeos.dev
On Tue, Mar 23, 2021 at 07:04:38PM -0700, Stephen Boyd wrote:
> Now that stacktraces contain the build ID information we can update this
> script to use debuginfod-find to locate the debuginfo for the vmlinux
> and modules automatically. This can replace the existing code that
> requires specifying a path to vmlinux or tries to find the vmlinux and
> modules automatically by using the release number. Work it into the
> script as a fallback option if the vmlinux isn't specified on the
> commandline.
One wish for the shell scripts: try to avoid bashisms as much as possible,
please.
--
With Best Regards,
Andy Shevchenko
HTML mail?
Quoting Konstantin Khlebnikov (2021-03-24 01:23:55)
> 24.03.2021, 05:04, "Stephen Boyd" <[email protected]>:
>
> Looks too noisy for me. Maybe print id in the line "Modules linked in:"?
> I suppose only out-of-tree modules need this?
>
Please see this note in patch 4:
Originally, I put this on the %pS format, but that was quickly rejected
given that %pS is used in other places such as ftrace where build IDs
aren't meaningful. There was some discussions on the list to put every
module build ID into the "Modules linked in:" section of the stacktrace
message but that quickly becomes very hard to read once you have more
than three or four modules linked in. It also provides too much
information when we don't expect each module to be traversed in a
stacktrace. Having the build ID for modules that aren't important just
makes things messy. Splitting it to multiple lines for each module
quickly explodes the number of lines printed in an oops too, possibly
wrapping the warning off the console. And finally, trying to stash away
each module used in a callstack to provide the ID of each symbol printed
is cumbersome and would require changes to each architecture to stash
away modules and return their build IDs once unwinding has completed.
Quoting Andy Shevchenko (2021-03-24 04:27:53)
> On Tue, Mar 23, 2021 at 07:04:38PM -0700, Stephen Boyd wrote:
> > Now that stacktraces contain the build ID information we can update this
> > script to use debuginfod-find to locate the debuginfo for the vmlinux
> > and modules automatically. This can replace the existing code that
> > requires specifying a path to vmlinux or tries to find the vmlinux and
> > modules automatically by using the release number. Work it into the
> > script as a fallback option if the vmlinux isn't specified on the
> > commandline.
>
> One wish for the shell scripts: try to avoid bashisms as much as possible,
> please.
>
I wish too but the script has /bin/bash at the start and I was trying to
follow similar style to what was already in here. Feel free to send a
patch to remove the bashisms.
On 3/24/21 9:55 AM, Christoph Hellwig wrote:
> On Tue, Mar 23, 2021 at 07:04:31PM -0700, Stephen Boyd wrote:
>> x5 : 0000000000000000 x4 : 0000000000000001
>> x3 : 0000000000000008 x2 : ffffff93fef25a70
>> x1 : ffffff93fef15788 x0 : ffffffe3622352e0
>> Call trace:
>> lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
>> direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> Yikes. No, please do not make the backtraces a complete mess for
> something that serves absolutely no need.
Would a "verbose" flag be acceptable solution? Something like write 1 to /sys/kernel/debug/verbose_stack to get the extra info.
I think I see a need for it.
On 3/24/21 3:04 AM, Stephen Boyd wrote:
> This series adds the kernel's build ID[1] to the stacktrace header printed
> in oops messages, warnings, etc. and the build ID for any module that
> appears in the stacktrace after the module name. The goal is to make the
> stacktrace more self-contained and descriptive by including the relevant
> build IDs in the kernel logs when something goes wrong. This can be used
> by post processing tools like script/decode_stacktrace.sh and kernel
> developers to easily locate the debug info associated with a kernel
> crash and line up what line and file things started falling apart at.
>
> To show how this can be used I've included a patch to
> decode_stacktrace.sh that downloads the debuginfo from a debuginfod
> server.
>
> This also includes some patches to make the buildid.c file use more
> const arguments and consolidate logic into buildid.c from kdump. These
> are left to the end as they were mostly cleanup patches. I don't know
> who exactly maintains this so I guess Andrew is the best option to merge
> all this code.
>
> Here's an example lkdtm stacktrace on arm64.
>
> WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
> Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE
> CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1
> Hardware name: Google Lazor (rev3+) with KB Backlight (DT)
> pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--)
> pc : lkdtm_WARNING+0x28/0x30 [lkdtm]
> lr : lkdtm_do_action+0x24/0x40 [lkdtm]
> sp : ffffffc0134fbca0
> x29: ffffffc0134fbca0 x28: ffffff92d53ba240
> x27: 0000000000000000 x26: 0000000000000000
> x25: 0000000000000000 x24: ffffffe3622352c0
> x23: 0000000000000020 x22: ffffffe362233366
> x21: ffffffe3622352e0 x20: ffffffc0134fbde0
> x19: 0000000000000008 x18: 0000000000000000
> x17: ffffff929b6536fc x16: 0000000000000000
> x15: 0000000000000000 x14: 0000000000000012
> x13: ffffffe380ed892c x12: ffffffe381d05068
> x11: 0000000000000000 x10: 0000000000000000
> x9 : 0000000000000001 x8 : ffffffe362237000
> x7 : aaaaaaaaaaaaaaaa x6 : 0000000000000000
> x5 : 0000000000000000 x4 : 0000000000000001
> x3 : 0000000000000008 x2 : ffffff93fef25a70
> x1 : ffffff93fef15788 x0 : ffffffe3622352e0
> Call trace:
> lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> full_proxy_write+0x74/0xa4
> vfs_write+0xec/0x2e8
> ksys_write+0x84/0xf0
> __arm64_sys_write+0x24/0x30
> el0_svc_common+0xf4/0x1c0
> do_el0_svc_compat+0x28/0x3c
> el0_svc_compat+0x10/0x1c
> el0_sync_compat_handler+0xa8/0xcc
> el0_sync_compat+0x178/0x180
> ---[ end trace 3d95032303e59e68 ]---
How will this work with the ftrace?
Quoting peter enderborg (2021-03-25 04:14:31)
> > el0_sync_compat_handler+0xa8/0xcc
> > el0_sync_compat+0x178/0x180
> > ---[ end trace 3d95032303e59e68 ]---
>
> How will this work with the ftrace?
>
It won't affect ftrace, if that's the question you're asking.
Quoting peter enderborg (2021-03-25 04:06:17)
> On 3/24/21 9:55 AM, Christoph Hellwig wrote:
> > On Tue, Mar 23, 2021 at 07:04:31PM -0700, Stephen Boyd wrote:
> >> x5 : 0000000000000000 x4 : 0000000000000001
> >> x3 : 0000000000000008 x2 : ffffff93fef25a70
> >> x1 : ffffff93fef15788 x0 : ffffffe3622352e0
> >> Call trace:
> >> lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> >> direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> > Yikes. No, please do not make the backtraces a complete mess for
> > something that serves absolutely no need.
It serves a need. Please look at the patches to understand that I'm
adding the buildid to automatically find the associated debug
information on distros.
>
> Would a "verbose" flag be acceptable solution? Something like write 1 to /sys/kernel/debug/verbose_stack to get the extra info.
>
> I think I see a need for it.
>
Or a kernel config option and a commandline parameter? That would be OK
for me as I said on v1 of this series. I'll add that in for the next
patch series given all the distaste for some more hex characters next to
the module name.
On Tue 2021-03-23 19:04:35, Stephen Boyd wrote:
> Let's make kernel stacktraces easier to identify by including the build
> ID[1] of a module if the stacktrace is printing a symbol from a module.
>
> Example:
>
> WARNING: CPU: 3 PID: 3373 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
> Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE hci_uart <modules trimmed>
> CPU: 3 PID: 3373 Comm: bash Not tainted 5.11 #12 a8c0d47f7051f3e6670ceaea724af66a39c6cec8
I tested it with "echo l >/proc/sysrq-trigger" and I got the following
output:
[ 71.905593] CPU: 0 PID: 1762 Comm: bash Kdump: loaded Not tainted 5.12.0-rc5-default+ #167 00000080ffffffff0000000000000000
00000000
It does not looks like an unique build-id.
Any idea what was going wrong?
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -91,6 +93,7 @@ const char *kallsyms_lookup(unsigned long addr,
>
> /* Look up a kernel symbol and return it in a text buffer. */
> extern int sprint_symbol(char *buffer, unsigned long address);
> +extern int sprint_symbol_stacktrace(char *buffer, unsigned long address);
> extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
> extern int sprint_backtrace(char *buffer, unsigned long address);
Could we use a more clear name? It is hard to guess what is
the difference between sprint_*_stacktrace() and sprint_backtrace().
What about sprint_symbol_build_id() ?
> diff --git a/kernel/module.c b/kernel/module.c
> index 30479355ab85..9e9cb502fb33 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2770,6 +2771,20 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
> }
> mod->core_kallsyms.num_symtab = ndst;
> }
> +
> +static void init_build_id(struct module *mod, const struct load_info *info)
> +{
> + const Elf_Shdr *sechdr;
> + unsigned int i;
> +
> + for (i = 0; i < info->hdr->e_shnum; i++) {
> + sechdr = &info->sechdrs[i];
> + if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
> + !build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
> + sechdr->sh_size))
> + break;
> + }
Just to be sure. Is this really reliable way how to find the build ID,
please?
> +}
> #else
> static inline void layout_symtab(struct module *mod, struct load_info *info)
> {
> @@ -2778,6 +2793,10 @@ static inline void layout_symtab(struct module *mod, struct load_info *info)
> static void add_kallsyms(struct module *mod, const struct load_info *info)
> {
> }
Best Regards,
Petr
On Thu 2021-03-25 16:21:46, Stephen Boyd wrote:
> Quoting peter enderborg (2021-03-25 04:06:17)
> > On 3/24/21 9:55 AM, Christoph Hellwig wrote:
> > > On Tue, Mar 23, 2021 at 07:04:31PM -0700, Stephen Boyd wrote:
> > >> x5 : 0000000000000000 x4 : 0000000000000001
> > >> x3 : 0000000000000008 x2 : ffffff93fef25a70
> > >> x1 : ffffff93fef15788 x0 : ffffffe3622352e0
> > >> Call trace:
> > >> lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> > >> direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e]
> > > Yikes. No, please do not make the backtraces a complete mess for
> > > something that serves absolutely no need.
>
> It serves a need. Please look at the patches to understand that I'm
> adding the buildid to automatically find the associated debug
> information on distros.
>
> >
> > Would a "verbose" flag be acceptable solution???? Something like write 1 to /sys/kernel/debug/verbose_stack to get the extra info.
> >
> > I think I see a need for it.
> >
>
> Or a kernel config option and a commandline parameter? That would be OK
> for me as I said on v1 of this series. I'll add that in for the next
> patch series given all the distaste for some more hex characters next to
> the module name.
IMHO, a build configure option would fit the best here.
It does not make sense to show the ID when the kernel vendor does
not have a service to download the related binaries. But it makes
sense to show the buildid by default when the provider/distro has
the service and want to use the ID when handling bug reports.
We could always add boot/run time options when people really need it.
Best Regards,
Petr
Quoting Petr Mladek (2021-03-30 03:29:24)
> On Tue 2021-03-23 19:04:35, Stephen Boyd wrote:
> > Let's make kernel stacktraces easier to identify by including the build
> > ID[1] of a module if the stacktrace is printing a symbol from a module.
> >
> > Example:
> >
> > WARNING: CPU: 3 PID: 3373 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm]
> > Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE hci_uart <modules trimmed>
> > CPU: 3 PID: 3373 Comm: bash Not tainted 5.11 #12 a8c0d47f7051f3e6670ceaea724af66a39c6cec8
>
> I tested it with "echo l >/proc/sysrq-trigger" and I got the following
> output:
>
> [ 71.905593] CPU: 0 PID: 1762 Comm: bash Kdump: loaded Not tainted 5.12.0-rc5-default+ #167 00000080ffffffff0000000000000000
> 00000000
>
> It does not looks like an unique build-id.
> Any idea what was going wrong?
Hmm not sure. What does 'hexdump /sys/kernel/notes' show or 'file
vmlinux' parse out of the kernel image?
>
> > --- a/include/linux/kallsyms.h
> > +++ b/include/linux/kallsyms.h
> > @@ -91,6 +93,7 @@ const char *kallsyms_lookup(unsigned long addr,
> >
> > /* Look up a kernel symbol and return it in a text buffer. */
> > extern int sprint_symbol(char *buffer, unsigned long address);
> > +extern int sprint_symbol_stacktrace(char *buffer, unsigned long address);
> > extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
> > extern int sprint_backtrace(char *buffer, unsigned long address);
>
> Could we use a more clear name? It is hard to guess what is
> the difference between sprint_*_stacktrace() and sprint_backtrace().
>
> What about sprint_symbol_build_id() ?
Sure.
>
>
> > diff --git a/kernel/module.c b/kernel/module.c
> > index 30479355ab85..9e9cb502fb33 100644
> > --- a/kernel/module.c
> > +++ b/kernel/module.c
> > @@ -2770,6 +2771,20 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
> > }
> > mod->core_kallsyms.num_symtab = ndst;
> > }
> > +
> > +static void init_build_id(struct module *mod, const struct load_info *info)
> > +{
> > + const Elf_Shdr *sechdr;
> > + unsigned int i;
> > +
> > + for (i = 0; i < info->hdr->e_shnum; i++) {
> > + sechdr = &info->sechdrs[i];
> > + if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
> > + !build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
> > + sechdr->sh_size))
> > + break;
> > + }
>
> Just to be sure. Is this really reliable way how to find the build ID,
> please?
>
The build ID is always part of a note section, so if we parse the notes
and find a build ID type of section (see nhdr->n_type == BUILD_ID) with
a GNU name then we know we have the right section and will be able to
parse the ID out of the buffer.